So I had an extra CZ75 mag hanging around begging me to do this, so I looked it up on the CZ forum (it is a sticky under the section CZ75 pistols) and tried it out. What you need to do is file the rear of the magwell both at the top, and bottom of the mag well (see pictures) to allow for the extra girth of the CZ75B magazines. File slowly, checking the CZ75B magazine every now and again, until it seats smoothly. My original CZ75 Pre-B magazines still seat well. I will be doing a function test ASAP.
I recommend fully stripping your pistol frame before doing this, it makes things much easier.
Here is a Pic of the top rear of the magwell that has been filed (notice the polished appearance). I still have to put some bluing onto it.

Here is a pic of the bottom rear of the magwell that has been filed.

Something interesting for those that are willing to try it.
I recommend fully stripping your pistol frame before doing this, it makes things much easier.
Here is a Pic of the top rear of the magwell that has been filed (notice the polished appearance). I still have to put some bluing onto it.

Here is a pic of the bottom rear of the magwell that has been filed.

Something interesting for those that are willing to try it.